The present invention relates to a method for determining the temperature of a fluid in a hydraulic arrangement for a motor vehicle.
The present invention furthermore relates to a hydraulic arrangement for a motor vehicle, having a pump arrangement, which is driven by means of a drive motor, having a pressure sensor, which is connected to a discharge port of the pump arrangement, wherein the pump arrangement is connected to a tank via a leakage point, and having a control unit, which is connected to the pressure sensor.
In the area of hydraulic arrangements for motor vehicles, the practice of connecting a pump to a power takeoff of an internal combustion engine is known. In this case, a discharge port of the pump is connected to a pressure control valve, by means of which a predetermined line pressure is generated. Respective control pressures for controlling actuators and the like are then derived from said line pressure by means of suitable additional valves.
Hydraulic arrangements of the abovementioned type in which a pump of a pump arrangement is driven by a drive motor in the form of an electric motor are furthermore known. In this case, a discharge port of the pump is preferably connected directly, i.e. without the interposition of pressure control valves or other proportional valves, to a port of an actuator, such as a piston/cylinder arrangement. The discharge port is furthermore connected to a pressure sensor. By adjusting the rotational speed of the drive motor, the fluid pressure of the hydraulic actuator and hence, for example, an actuating force for actuating a clutch of a motor vehicle drive train or the like can be adjusted. This is preferably accomplished by means of a control operation in which the rotational speed is adjusted as a function of the signal of the pressure sensor.
In order to improve controllability in the case of “pump actuators” of this kind, the discharge port of the pump is furthermore connected to the tank via a leakage point. This leakage point can be implemented by means of an orifice plate, for example.
The fluid used in hydraulic arrangements of this kind has a viscosity which is dependent on temperature. In order to further improve the controllability of the hydraulic arrangement, the preference is therefore for measuring the temperature of the fluid by means of a temperature sensor.